Austin Roorda: How the unstable eye sees a stable and moving world
Talk by Austin Roorda, School of Optometry, UC Berkeley. Given to the Redwood Center for Theoretical Neuroscience at UC Berkeley.
Audio/Visual sound, color
How is it that the eye can have an exquisite sense of motion even while the retinal image of the stable world during fixation is in constant motion? Several hypotheses have arisen: The “efference-copy” hypothesis holds that efferent signals derived from the opto-motor control circuitry are used to exactly offset the image instability induced by eye-motion 1. The “data-driven” hypothesis holds that image stabilization is computed from the content of the images, deriving compensatory information from the displacement of image features over time 2. Or, we might just suppress the lowest common motion of any visual scene 3. In any case, the physiology underlying this phenomenon remains largely unknown. Recent experiments from our lab using an adaptive-optics-based eye tracker have revealed that the percept of motion bears a different relationship to actual eye-motion than any extant hypothesis predicts. We found that stimulus motions that have directions which are consistent with eye-motion, but largely independent of magnitude of that motion, produce the most stable percepts. These new observations not only challenge all existing theories but, more importantly, define a simpler path toward a physiological solution. 1. Helmholtz,H. Helmholtz's Treatise on Physiological Optics. Optical Society of America, Rochester (1924). 2. Poletti,M., Listorti,C. & Rucci,M. Stability of the visual world during eye drift. J. Neurosci. 30, 11143-11150 (2010). 3. Murakami,I. & Cavanagh,P. A jitter after-effect reveals motion-based stabilization of vision. Nature 395, 798-801 (1998).